The objective of this research proposal is to determine the potential of the mammalian retina for repair via endogenous mechanisms. In response to retinal damage, Muller glial (MG) cells of several vertebrate model systems have been shown to give rise to new retinal neurons. However, in mammals, there is a paucity of data directly testing the regenerative capacity of MG cells in vivo. Our central hypothesis is that, in response to retinal damage, mature mouse MG cells possess the ability to re-enter the cell cycle and trans-differentiate into retinal neurons. The overall goal of this proposal is to test this hypothesis by performing genetic, Cre-loxP fate mapping experiments and time lapse imaging. Aim 1. Determine the capacity of mouse Muller glial cells to give rise to mature retinal neurons within specific environmental contexts. We will test the hypothesis that retinal Muller glial (MG) cells have the ability to regenerate retinal neurons by chemically inducing neuronal degeneration and performing in vivo Cre-loxP fate-mapping experiments. We will also test the hypothesis that MG cell regenerative potential is significantly hindered as a consequence of a non-permissive retinal environment due to glial scarring. Here, we will perform the same fate-mapping experiment, but within the genetic background of Vimentin-/-;Gfap-/- mutant mice known to exhibit a retinal environment substantially more supportive of neuronal transplantation. Aim 2. Elucidate the cellular mechanisms of the Muller glial response to retinal damage and subsequent trans-differentiation events. We hypothesize that, in response to damage, a discrete subset of MG cells re-enter the cell cycle and translocate apically toward the outer limiting membrane of the retina where they undergo mitosis before translocating to the appropriate lamina as differentiating neurons. To test this hypothesis, we will perform live imaging of damage-induced retinal explants in which MG cells are fluorescently labeled. RELEVANCE Neuronal degeneration lies at the heart of a spectrum of debilitating human cognitive and motor diseases including Alzheimer's and Parkinson's disease as well as sensory diseases such as blindness. By characterizing cell populations within the retina, which have the ability to generate new neurons, therapeutic approaches could be employed to harness the ability of these cells to cure human neurological diseases.